linux-kernel - Re: [PATCH v2] KEYS: prevent NULL pointer dereference in find_asymmetric

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Message-Id: <D44D89US0PW6.3HVNXUTP0CMFZ@kernel.org>
Date: Thu, 12 Sep 2024 17:12:26 +0300
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "Sergey Shtylyov" <s.shtylyov@....ru>, "Roman Smirnov"
 <r.smirnov@....ru>, "David Howells" <dhowells@...hat.com>, "Herbert Xu"
 <herbert@...dor.apana.org.au>, "David S. Miller" <davem@...emloft.net>,
 "Andrew Zaborowski" <andrew.zaborowski@...el.com>
Cc: <keyrings@...r.kernel.org>, <linux-crypto@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <lvc-project@...uxtesting.org>
Subject: Re: [PATCH v2] KEYS: prevent NULL pointer dereference in
 find_asymmetric_key()

On Wed Sep 11, 2024 at 5:45 PM EEST, Sergey Shtylyov wrote:
> On 9/11/24 4:19 PM, Jarkko Sakkinen wrote:
>
> [...]
>
> >>>>> In find_asymmetric_key(), if all NULLs are passed in id_{0,1,2} parameters
> >>>>> the kernel will first emit WARN and then have an oops because id_2 gets
> >>>>> dereferenced anyway.
> >>>>>
> >>>>> Found by Linux Verification Center (linuxtesting.org) with Svace static
> >>>>> analysis tool.
> >>>>
> >>>> Weird, I recall that I've either sent a patch to address the same site
> >>>> OR have commented a patch with similar reasoning. Well, it does not
> >>>> matter, I think it this makes sense to me.
> >>>>
> >>>> You could further add to the motivation that given the panic_on_warn
> >>>> kernel command-line parameter, it is for the best limit the scope and
> >>>> use of the WARN-macro.
> >>>
> >>>    I don't understand what you mean -- this version of the patch keeps
> >>> the WARN_ON() call, it just moves that call, so that the duplicate id_{0,1,2}
> >>> checks are avoided...
> >>
> >> I overlooked the code change (my bad sorry). Here's a better version of
> >> the first paragraph:
> >>
> >> "find_asymmetric_keys() has nullity checks of id_0 and id_1 but ignores
> >> validation for id_2. Check nullity also for id_2."
> >>
> >> Yep, and it changes no situation with WARN_ON() macro for better or
> >> worse. It would logically separate issue to discuss and address so
> >> as far as I'm concerned, with this clarification I think the change
> >> makes sense to me.
> > 
> > Actually explicitly stating that call paths leading to WARN_ON()
> > invocation are intact by the commit (as a reminder for future).
>
>    OK...
>    Do you still think the Fixes tag should be dropped (and thus the
> Reported-by tag would become unnecessary?)?

Good question but I think we should keep them (spent 15 minutes thinking
about this).

It's a glitch at least and would not do harm for stable series to have
it like that :-) So if you polish the message, send a new version I'll
pick it, and put to my next PR.

Thanks for the patience with this.

>
> > BR, Jarkko
>
> MBR, Sergey

BR, Jarkko